Soxroc  Extraction Unit The OPSIS LiquidLINE SoxROC Extraction Unit is an automated Soxhlet instrument that can extract fat according to official methods. The instrument is based on Randall and Twisselmann techniques, using hot solvents and a closed system to reduce extraction time versus manual Soxhlet. The SoxROC follows officially approved methods for fat extraction. The SoxROC is designed to be flexible and is therefore also capable of extractions using other solvents.